In general, supercapacitors improve storage density through the use of a porous material that increases the specific area of the electrodes. There has been interest in using carbon-based nanomaterials as supercapacitor electrodes due to several advantages of carbon, such as light weight, high electrical conductivity, and electrochemical surface area1-20. Activated carbon (AC) has received a lot of attention and has been used in supercapacitor design as a good electrode material due its high surface area. It is currently the material of choice for both low and high voltage applications. However, with AC, the use of binders and conducting agents, the particulate nature of AC, the presence of uncontrolled functional groups, and the ill-defined structure of AC powders hinder the capacitance and result in long-term degradation. Recently, other types of carbon materials such as carbon aerogel. carbon black, carbon nanotubes (CNTs) and graphene have been used for the study of improved supercapacitors. High surface area in these carbon materials is generally characteristic of highly developed nanostructure. Nanomaterials can also have controlled chemical composition and tailored physical architectures down to nanoscale dimensions. They are randomly oriented with respect to the current collectors in a stacked geometry in supercapacitors. In such a case, these carbon materials are unfavorable for electrolyte wetting and rapid ionic motions because the electrolyte ions are often limited from penetrating far inside the graphitic planes.
There would be a large number of interesting new designs for energy storage devices if carbon electrodes could be tailored and engineered in forms that would avoid the problems outlined above.